1. Field of the Invention
The present invention relates to a method of mounting a plurality of semiconductor elements on a wiring board.
2. Description of the Related Art
When a plurality of semiconductor elements are joined to a wiring board by face down bonding, the following method has been carried out conventionally. That is, the plurality of semiconductor elements are mounted on the wiring board by pressing the plurality of semiconductor elements having bump electrodes with soldering bumps formed thereon to the wiring board while aligning the electrodes to fix them temporarily and then heat-melting the soldering bumps.
As the heat produced in the semiconductor element thus mounted is compelled to escape via the bump electrodes toward the wiring board, the thermal resistance has been extremely high.
This has posed a serious problem particularly when the power consumption of such a semiconductor element is large.
As a result, there has generally been employed a method of providing a heat sink as a radiation path for semiconductor elements ("Handbook of Semiconductor Mounting Technique" compiled by Koshi Nihei, Masao Hayakawa and Fumio Miyashiro, K. K. Science Forum (1986)).
However, the above method is still problematical because the heat sink is joined to a plurality of semiconductor elements after the elements are joined to a wiring board by face down bonding. In other words, slants of the semiconductor elements, variations of their thickness and the like tend to cause bad contact between the heat sink and the semiconductor elements.